Exhaust valve stem shield



March 28, 1 933.

D. F. ASBURY EXHAUST VALVE STEM SHIELD v Filed May 6, 1931 jans-ey jlsburg/ Patented Mar. 28, 1933 DoRsEY F. AsBURY, E BnooMEs ISLAND, MARYLAND EXHAUST VALVE STEM: SHIELD Application led May 6, 1931.

My invention relates to an internal combustion engine which includes an exhaust port having entrance and discharge ends, the former of which is controlled by a poppet valve, and has for its purpose the provision of means for shielding from the gas current only that side of a length of the valve stem which is remote from the discharge end of the port and which would otherwise be directly exposed to such current in the port, my

present application constituting a continuation in part of my prior application 528,941, filed April 9, 1931.

I will describe my invention as applied to an overhead valve engine7 but it will be apparent that the same can be employed in the exhaust port of a side valve or a horizontal valve engine and that the same is susceptible to changes and variations by the exercise of ordinary mechanical skill without departing from the scope thereof.

In the drawing chosen to illustrate my invention, the scope whereof is set forth in the appended claims,

Figure 1 is a vertical section of the upper end of a cylinder of an internal combustion engine showing an exhaust port and a poppet valve in open position and my invention in association therewith;

Figure 2, a section on line 2--2 of Fig. 1; and

Figure 3, a section on line 3-3 of Fig. 1.

Referring in detail to the drawing, A indicates generally a cylinder head of an internal combustion engine having an exhaust port 10 controlled by a poppet valve B whose stem l1 is slidably mounted in a bearing 12 in the upper end of the head A. The valve is moved to its open position by a rocker arm, 40 the end 13 of which is shown against the end of the valve stem. A coil spring 14 moves the valve to closed position. The exhaust port 10 has the usual exit 15. Inside of the port I provide a baille flange 16 cast integral with the cylinder head to guard the flow of Serial No. 535,525.

exhaust gases from a longitudinal portion of the side of the valve stem. The flange 16 is in the same currentlines of theexhaust gas stream as the valve stem and in frontfof the stem with respect to the direction of flow of the exhaust gas current. The side surfaces 17 ofthe flange 16 are shown in Figure 2 slightly concave, but they may bellat, while theend 18 of the flange is pointed as shown in Figure 3. The flange 16 divides and di- 55 vertsv exhaust gases from a portion of the valve stein between the valve head and said bearing that would otherwise be baffled by saidstem portion. The use of the concave side `faces 17 assists in this diversion of ex- 60 haust gases from the valve stem by-directing the gases moving from the said faces away from the valve stem as will be apparent from Figure 2. The portion of the valve stem from the head of the valve to the flange 16, due to the flow of the exhaust gases crossing the stem will be heated more ony the side the gases directly strike previous to crossing the stem and the extra expansion on this h otter side ofthe stem produces in the latter a slight bend or warpwhich would, if not counteracted by an oppositelyopposed warp, throw thevalvehead both off' center and out of level with its seat on the head A. However, such opposed warp is produced by the extra expansion in the hotter side of the stemwhich is remote from the flange 16. The flange 16 can be made'of such width and length so that the valve head will be maintained exactly central with Arespect to its seat on the cylinder headwand substantially level at all times. Another purpose of the flange 16 is to de# crease the amount of heat imparted tothe valve stem, so that'it will work better inits bearing 12 and permit of a ysmaller tappet 85 clearance.k Y

I, Without the fla-nge 16 the whole side of the valve stemin the port is heated hotter on the side against which the exhaust directly impinges and the extra expansion of that hotter side produces a bend or warp in the direction toward the exit l5 which positions the valve head considerably olf center and out of level with respect to its seat on the cylinder head and therefore the valve has to seat tight on the portion nearest the port exit and loose on the portion farthest from the port exit and the leak occurs at the loose seating portion. Almost invariably where exhaust valves have been burned, the burning occurred on the portion of the valve which was farlhest away from the exit of the exhaust port.

Gases of explosion are hottest and under highest pressure during the power stroke of the engine and where the valve permits a leak, large quantities of the hot gases escape by the very small leaky surface and impart too much heat to the small surface and it is therefore burned and then the amount of burn increases for the same reason. Valves of the customary size per piston displacement do not burn until the valve permits a leak during the power stroke of the engine. It is extremely important that the head of the valve should approach its seat both centrally and level with respect thereto and my invention provides simple and non-machined means for maintaining the valve head in the correct alinement and relation to its seat, which prevents the valve from being burned.

I claim:

l. In a gas engine structure, a cylinder includng a gas port having entrance and discharge ends, a poppet valve controlling the entrance end of the port, said valve including a head and a stem with the latter having a length thereof exposed to gas current in the port, and means shielding from the gas current only that side of the exposed length of the stem which is remote from the discharge end of the port.

2. In a gas engine structure, a cylinder including a gas port having entrance and discharge ends, a poppet valve controlling the entrance end of the port, said valve including a head and stem with the latter having a length thereof exposed to gas current in the port, and means interrupting the gas current to maintain an eddy in said current, at that side only of the exposed length of the stem which is remote from the discharge end of the port, during the presence of gas current in th-e port.

3. In a gas engine structure, a cylinder including a gas port having entrance and discharge ends, a poppet valve controlling the entrance end of the port, said valve including a head and a stem with the latter having a length thereof exposed to gas current in the port, and means on the cylinder shielding from the gas current only that side of the exposed length of the stem which is remote from the discharge end of the port.

Ll. In a gas engine structure, a cylinder insignature.

DORSEY F. ASBURY. 

